Despite established Links to longevity, the role of conscientiousness in the health process has not been systematically studied, nor have the effects of aging on the relationship between conscientiousness and health been investigated. Two longitudinal studies are proposed to test the relationship between conscientiousness and the social environmental factors and health-related behaviors that contribute to health and longevity. Pilot data are reported which suggest that a comprehensive model of conscientiousness is linked to many of the health behaviors and social environmental factors that contribute to health and longevity. Also, data is presented showing significant increases in conscientiousness and decreases in risky health behaviors with age. Building on these initial findings, the proposed research has three aims. The first aim is to fully delineate the relationships among conscientiousness, health-related behaviors, and the social environmental factors that affect health and longevity using multiple methods. The second aim is to test how age affects the relationships among conscientiousness, health-related behaviors, and social environmental factors. The third aim is to perform follow-up assessments of two age-stratified samples in order to test the relationship between changes in conscientiousness and changes in the health behaviors and social environmental factors that contribute to better health. The proposed research is significant for four reasons. First, conscientiousness, through its relationship to health behaviors and social environmental factors, may be one of the most important, yet under-appreciated contributors to positive health outcomes across the life course. Second, the effect of age on the relationship of conscientiousness to these health factors is unknown and the proposed studies will provide the most definitive test of the effect of aging on these relationships. Third, increases in conscientiousness across the life course may facilitate even greater improvements in health behaviors and social environmental factors that, in turn, contribute to positive health outcomes. And fourth, this research will allow us to identify the social environmental factors that promote increases in conscientiousness and decreases in risky health behaviors.